A Mutation in the Chemical Defense Pathway of Erysimum cheiranthoides (Brassicaceae) Reduces Total Cardenolide Abundance

Erysimum cheiranthoides L (Brassicaceae; wormseed wallflower) accumulates not only glucosinolates, which are characteristic of the Brassicaceae family, but also abundant and diverse cardenolides. These steroid toxins, primarily digitoxigenin, cannogenol, strophanthidin, and their glycosylated forms, inhibit the function of essential Na+/K+-ATPases in animal cells. We screened a population of 659 ethylmethanesulfonate-mutagenized E. cheiranthoides plants to identify isolates with altered cardenolide profiles. One mutant line exhibited 66% lower cardenolide content, resulting from greatly decreased cannogenol- and strophanthidin-derived cardenolides, partially compensated for by increases in digitoxigenin-derived cardenolides.